In a wireless communications system, within a coverage area of a base station, when users at different locations use a same transmission medium to perform uplink access, the base station needs to use a multiple access technology to distinguish between different user signals. For example, using Sparse Code Multiple Access (SCMA) technology, which is a hybrid multiple access technology combined by Time Division Multiple Access (TDMA), Frequency Division Multiple Address (FDMA) and Code Division Multiple Access (CDMA), users at different locations within a same area may use a same time-frequency resource block to perform uplink access and data transmission.
In the existing technology, before sending an uplink data signal to a base station, a terminal first needs to initialize the uplink access, to keep the terminal and the base station synchronized. Then, the terminal sends an uplink resource request message to the base station. After receiving the uplink resource request message, the base station generates an uplink resource allocation message, and sends the uplink resource allocation message to the terminal. After receiving the uplink resource allocation message from the base station, the terminal generates an uplink data signal and a pilot signal. The terminal sends, on an uplink resource block allocated by the base station, the uplink data signal. In other words, regardless of a volume of uplink service data, the terminal needs to interact with the base station to generate an uplink data signal and a pilot signal. However, with the emergence of real-time online services and machine-type communications (MTC) services, a communication between a terminal and a base station tends to be short and a volume of uplink service data tends to be small. In this case, before the uplink service data is transmitted, resources occupied in the foregoing interaction between the terminal and the base station may be more than resources occupied for transmitting the uplink service data. Therefore, when a volume of the uplink service data sent from the terminal to the base station is relatively small, resources are wasted on the multiple interactions between the terminal and the base station for generating an uplink data signal and a pilot signal.